The long range goal of this project is the application of molecular genetic tools to understanding the cellular mechanisms and processes that are necessary for differentiation and morphogenesis. The objective is to identify, isolate and characterize genes that are essential for development of Dictoyostelium discoideum. This eucaryotic amoebal organism provides a unique model system for the study of cellular functions that are involved in development. During development, a uniform population of amoebal cells differentiates into a multicellular organism consisting of two cell types with a highly regulated spatial organization. Motility, signal transduction, adhesion, morphogenetic signalling and cell type specific gene regulation are among the fundamental processes utilized by this organism to accomplish its developmental program. The information gained about how these functions are accomplished in Dictyostelium will provide clues to similar functions in other organisms. An indirect genetic approach to understanding the cellular processes related to development will be taken. Mutants that affect processes that are essential for development will be identified, and then the genes that were mutated will be isolated. In this way, a direct handle on critical functional elements can be gained. Mutants that affect development are not new in Dictyostelium, but the means to isolate the mutated genes has never been available. The DNA mediated transformation system will provide the means for both mutating and isolating these genes. Two approaches to accomplishing this goal will be undertaken in parallel. Antisense RNA synthesized from a transformation vector will be used to inhibit expression of essential developmental genes, or a vector that inserts into the chromosome will be used to interrupt gene expression. In both cases, large numbers of transformants will be screened for defects in morphogenesis caused by the transformation vector. The vector sequence will then provide the means for isolating the inactivated gene. The purpose of this project is not simply to clone more genes to study their regulation. Rather it is to use functional criteria to isolate important genes as a means to eventually studying the function of the gene products.